Hello,
I had this problem and fixed it. To describe the issue; in dedicated, the owning client would falsely predict his own movements and get the forced network update RPC producing a jitter movement without correct rotation.
The simple solution is to enable client navmesh in your project settings and to call move to on the owning client and server only… (see image)
I have provided a paste that you can put in your ThirdPerson character template project and see it working.
Press T to navigate to the spot in the middle of the screen.
This is not a great solution, but it will get you moving.